Row crops, including lettuce, cabbage, kale, chard, and the like, are typically harvested by hand. This procedure involves several steps, each typically done manually. These manual steps include cutting the headed produce from the stem, which is imbedded in the ground, removing any dehiscent, exfoliant or damaged external leaves, and loading the cut heads into some form of box or bin. The term dehiscent, as used herein refers to those leaves of the produce which have opened away from the head, and are generally not suitable for harvesting. In some lettuce harvesting operations, the roughly cleaned lettuce previously discussed is loaded into bulk crates for final packing at an off-field location. Alternatively, some traditionally packaged lettuce (whole lettuce) is wrapped in the field and packed in the shipping crates which are ultimately delivered to the greengrocer. In each of these methods, a portion of the stem, hereafter referred to as the core to which the lettuce leaves are attached, remains with the headed lettuce through harvesting, packing, shipping and eventual purchase by the consumer.
Recent marketing trends for many forms of produce, wherein the produce is to some extent processed by the packer to make it easier to use by the consumer, have received exceptional acceptance in the marketplace. One well-known example of such value-added produce is the prepared lettuce or prepackaged salad mix currently available in many markets. The previously discussed prior art harvesting methods, well suited to headed lettuce, do not provide a produce product optimally suited for value-added produce shippers who sell this form of lettuce. In particular, the core, so laboriously harvested with the lettuce leaves, must be removed or extracted from the leaves before they can be processed into lettuce mix at the packing facility.
The core must be removed not only for aesthetic reasons so that the salad mix appeals to the consumer, but also so that the core, being much denser than the leaves, is not packaged with the leaves. Because packaging systems used in the value-added produce industry often utilize measured weight of the product to determine package fill, core material incorporated in the salad mix is not only unaesthetic, but significantly reduces the amount of lettuce leaf in the package. For these reasons, it is important that core material be omitted from packaged salad mixes. Of course, removing the core, if harvested in the field and delivered to the packer, engenders additional expense. Lettuce which is harvested for value-added produce packers should therefore optimally arrive at the packing facility without dehiscent leaves or cores.
Exemplary of these prior art harvesting methods is U.S. Pat. No. 3,827,503 to Hansen ("Hansen"). Hansen teaches a tractor-mounted harvesting machine for cabbage and the like. The harvester taught therein uses ". . . stabilizing means located below said conveyor means for engaging said root to stabilize said root while it being conveyed . . . " (claim 1), and ". . . base means to engage opposites sides of said stem and pull said head downwardly on said spaced elongated rail means . . . " (claim 9) (emphasis added). Hansen is seen therefore to use the stem of the produce, which is removed from the earth with the head, to guide the produce through the conveyor means taught therein. Accordingly, Hansen does not teach any means for separating the produce from its core, nor does this reference note any benefit in doing so.
U.S. Pat. No.4,211,061 to Richey teaches a flexible crop pickup device well suited to the harvesting of tomatoes. Richey also teaches no means for separating the produce from its core. Suited as this invention is to the harvesting of tomatoes and the like, it teaches "Any of a number of devices may be used with the disks to sever the plant stems when required." Similarly, U.S. Pat. Nos. 5,174,093 to Rodriguez ("Rodriguez") and 4,156,465 to Porter ("Porter") teach apparatus for harvesting above-ground crops without respect to the specific feature of removing the core thereof during the harvesting process, as taught by the present invention. Porter teaches a harvester conveyor having ". . . a system for keeping the conveyor links free from rocks, chunks of dirt, mud and other foreign matter . . . " Rodriguez is concerned with the non-destructive harvesting of crops. The invention taught therein is specifically designed to "strip the crop from the plants while leaving the plants in a relatively undisturbed condition after they have been picked." Again, neither Rodriguez nor Porter appreciate the benefit of separating the produce from its core, nor teach a specific method for doing so.
Accordingly, it would be desirable to provide a method for harvesting row crops, including lettuce and most particularly iceberg or other forms of headed lettuce and an apparatus to perform that method where the core is removed from the head during the harvesting process. Moreover, it would be desirable if such harvesting were faster and less costly than the currently used manual processes described elsewhere herein.
Furthermore, it would be desirable if the apparatus for practicing the method were convertible from a harvesting method delivering cored lettuce to a similarly automated method which delivers lettuce with the cores intact for shipment as head lettuce.